1. Field of Invention
This invention relates to the field of providing electricity to a power grid, particularly whenever the electricity is generated via solar panels (e.g., photovoltaic electricity generation).
2. Background
Electricity may be generated in many ways. Frequently, electricity is generated via converting mechanical energy or solar energy into electrical energy.
Known methods for converting mechanical energy into electrical energy have not been entirely satisfactory for electricity generation and storage. For example, using the mechanical energy resulting from high pressure steam to generate electricity via a reciprocating or steam engine is unsatisfactory since (1) the production of high pressure steam requires heat from combusting fossil fuels or nuclear fission and (2) such heat production methods have deleterious effects on earth's environment (e.g., carbon emissions from combusting fossil fuels may contribute to global warming and nuclear waste resulting from nuclear fission can render geographical areas uninhabitable due to radioactivity). For another example, using the mechanical energy of moving fluids (e.g., wind and flowing or falling water) to turn the turbine of a generator is unsatisfactory since, among other things, (1) natural winds and water flows are unpredictable and (2) unnatural falling water frequently requires the building of a damn which can be expensive and damaging to the natural environments surrounding the damn. The unsatisfactory aspects of converting mechanical energy into electrical energy have resulted in a focus on electrical energy generation from solar energy, which is considered one of most environmentally friendly and safest energy sources. See, e.g., the country of Germany which has announced that it will completely abandon nuclear energy by 2022 in view of the 2011 Fukushima Daiichi Nuclear Power Plant meltdown in Japan; see also the California Public Utilities and Federal Energy Regulatory Commissions which estimate that solar energy could be used to make 3000 MW (MegaWatts) of electrical power in California by the year 2016 (i.e., about 6 percent of the electrical power the state has ever used in one time, which was 50,000 MW back in 2006).
One way to convert solar energy into electrical energy is via photovoltaics (PV). Typically, photovoltaics may be accomplished by exposing at least one panel of semi conductors that exhibit the photovoltaic (PV) effect to sunlight to produce direct current electricity. Often, the electricity produced by distributed pluralities or arrays of PV panels is combined and provided to the public power grid (i.e., electricity network). Although useful for producing electricity, photovoltaics have not yet been entirely satisfactory for converting solar energy into electrical energy for a variety of reasons.
One problem with photovoltaics is that the amount of electrical energy generated by each one of the PV panels in a distributed plurality or array of PV panels depends on uncertain environmental factors (e.g., weather) which can cause undesirable fluctuations in the voltage of the power grid (voltage fluctuations unfavorably affect the deliverability of grid loads and overall managability of the power grid). For example, the electrical production of a plurality of PV panels under moving clouds can change from very little to very large amounts in a short time period, which change will correspondingly cause a voltage fluctuation in the associated power grid. The identified voltage fluctuation problem is exacerbated by the uncertainty of draws on the electrical energy within the power grid, for instance, whenever high power consumption by households accessing the grid coincides with low power production from the PV panels or whenever low power consumption coincides with high power production. Accordingly, there is a need for systems and methods of converting solar energy into electrical energy without resulting in unfavorable voltage fluctuations in the power grid.
One attempt to reduce voltage fluctuations in the power grid is embodied by the advanced metering infrastructure (AMI) employed by the Sacramento Municipal Utility District (SMUD) in California. The AMI is a control system that predicts draws on the grid based on historical electricity consumption and power generation. With reference to photovoltaics, the AMI is suited for reducing the exacerbating effects of uncertain energy draws on the grid but the AMI does nothing to combat the environmental and other uncertainties associated with photovoltaic production of electrical energy. Accordingly, a need remains for systems and methods of converting solar energy into electrical energy without resulting in unfavorable voltage fluctuations in the power grid.
Another attempt to reduce voltage fluctuations in the power grid caused by photovoltaic production of electrical energy is numerical simulation. See U.S. Dept. of Energy, High Penetration Solar Forum, “Planning & Modeling for High penetration Solar” and “Solar Variability, Forecasting, and Modeling Tools.” Numerical simulation uses historical data to predict electrical energy inputs to the power grid (electrical energy sources may include a plurality or array of PV panels). While better than nothing, this approach cannot accurately account for environmental and other uncertainties associated with photovoltaic production of electrical energy.
Yet still, another attempt to reduce voltage fluctuations in the power grid caused by photovoltaic production of electrical energy is battery storage (see, e.g., U.S. Pub. Pat. App. No. 2003/0047209 (published Mar. 13, 2003). Known battery storage techniques sometimes involve storing all the electricity produced by a plurality or array of PV panels in a high capacity or long term battery so that the electrical energy may be provided to the grid at a known rate. Although effective at reducing voltage fluctuations in the grid, this approach is unsatisfactory since high capacity or long term batteries are expensive and have low transmission efficiency. Thus, a need still exists for systems and methods of converting solar energy into electrical energy without high capacity or long term battery storage and without resulting in unfavorable voltage fluctuations in the power grid.